Befunge

Nobody said text HAD to go left to right

Befunge source code looks like this

Fibonnaci:

0:09p1>09g\:09p+:.84*,v
     ^               <

DNA (68 As, Cs, Gs, and Ts):

vDN>"A"v
>#v?"C"v
  v>"G"v
@ >>"T"v
|!p01-<,
 10g:1^>

Why do I love it so much?

It is a two dimensional programming language…

and IT CAN MODIFY ITS OWN SOURCE CODE WHILE IT IS RUNNING